P423: ACUTE MYELOID LEUKEMIA REPROGRAMS LIPID METABOLISM BY DOWNREGULATING CD36 EXPRESSION IN HEPATOCYTES.
Authors: Rebecca Maynard, Katherine Hampton, Charlotte Hellmich, Martha Ehikioya, Dominic Fowler-Shorten, Kristian Bowles, Stuart Rushworth
Journal: HemaSphere (2023)

Background: Acute myeloid leukemia (AML) is a highly proliferative disease, which requires high metabolic turnover to allow for constant expansion. We and others have previously shown that primary human AML blasts rely on fatty acid (FA)-oxidation for survival and proliferation. More recently, FA metabolism has been shown to be upregulated in AML and confers resistance to treatments such as venetoclax with azacytidine. The liver has a key role in lipid metabolism and can receive dietary FA, and free fatty acids (FFA) from adipose tissue, which are oxidised, to produce energy in the form of, ATP or ketone bodies. Liver FFA oxidation is induced by the hormone mediated release of FFA from adipose stores and subsequent uptake into hepatocytes. Aims: The aim of this project was to determine if AML can alter FA metabolism in the liver to support disease progression and by what mechanism. Methods: Tail vein injections of AML cells HOXA9/Meis1 and MN1 were used to engraft C57Bl/6 mice. After sacrifice blood, BM, liver and fat pads were isolated and analyzed. Flow cytometry confirmed AML progression in the blood and bone marrow and infiltrating AML in the fat pads and liver. qRT-PCR was performed on liver cells from control and AML mice to investigate changes in genes associated with FA metabolism. Next we isolated primary hepatocytes from C57Bl/6 mice and cultured with conditioned media from MN1 AML cells and examined gene expression changes. Seahorse XFp cell mito stress test analysis was performed on primary hepatocytes. Finally, primary hepatocytes were also cultured with the addition of BODIPY C16 long chain FA, in control media, conditioned media or with MN1 AML cells on transwells. Results: We first studied the effect of AML progression on weight, fat deposits and FFA plasma levels in host animals. Weight of animals is stable over the initial period of AML progression but reduces during the later stages of AML disease. Fat deposits in the epididymal and inguinal stores were smaller in AML mice. Moreover, elevated plasma FFA were observed in AML mice compared to control mice. These data support the notion that AML induces lipolysis in white adipose tissue fat compartments. qRT-PCR analysis of RNA isolated from liver samples showed reduced expression of genes associated with fatty acid metabolism, such as CD36, CPT1, HMGCS2, PPARy and ACADM. In vitro analysis of primary hepatocytes cultured with either MN1 or HOXA9/Meis1 in transwells showed downregulation of CD36 and CPT1 indicating that AML directly regulates expression of liver genes associated with FA metabolism. Analysis of mitochondrial stress in primary hepatocytes showed decreased reliance on FA oxidation by using the CD36 inhibitor SSO and ETO suggesting AML dampens hepatocyte FA metabolism. To determine the role of AML in fatty acid uptake by primary hepatocytes we treated them with of BODIPY conjugated C16 long chain FA to track FFA uptake. Representative images show that uptake of BODIPY conjugated C16 long chain FA is reduced in AML treated hepatocytes compared to controls. These data suggest that AML is able to redirect FFA away from the liver by down regulating CD36 which mediates FFA uptake in the liver. Summary/Conclusion: We find that AML alters the expression of genes associated with FA metabolism in the liver. Our in vivo and in vitro studies indicate that AML cells secrete cytokines which reduce CD36 and CPT1 expression in hepatocytes and thus the FA metabolism in the liver. Increasing our understanding of how AML is able to access large amounts of metabolites, allowing the disease to successfully infiltrate and expand throughout healthy BM, may aid in the development of novel therapeutic targets. Keywords: Lipid metabolism, Acute myeloid leukemia, Liver